Multiline syntax for piping a heredoc; is this portable?

Question

I\'m familiar with this syntax:

cmd1 << EOF | cmd2
text
EOF

but just discovered that bash allows me to write:

cmd1 &         


        

Answer 1

Yes, the POSIX standard allows this. According to the 2008 version:

The here-document shall be treated as a single word that begins after the next and continues until there is a line containing only the delimiter and a , with no characters in between. Then the next here-document starts, if there is one.

And includes this example of multiple "here-documents" in the same line:

cat <

So there is no problem doing redirections or pipes. Your example is similar to something like this:

cat file |
cmd

And the shell grammar (further down on the linked page) includes these definitions:

pipe_sequence    :                             command
                 | pipe_sequence '|' linebreak command

newline_list     :              NEWLINE
                 | newline_list NEWLINE
                 ;
linebreak        : newline_list
                 | /* empty */

So a pipe symbol can be followed by an end-of-line and still be considered part of a pipeline.